The invention discloses a preparation method of delta-lactone with high purity, the preparation method has simple operation, and low cost and is carried out according to the following steps: taking a compound I with a structural formula as above, mixing with acrylic acid, organic amine, methanol, benzoic acid and hydroquinone, stirring the mixture in a high-pressure reaction vessel at the temperature of 100 DEG C-250 DEG C for generating a compound II, carrying out decompression dehydration on the compound II, mixing the residue with the same mole of boric acid, gradually increasing the temperature till no carbon dioxide is exhausted, pouring reaction solution into water, using methyl tert-butyl ether for extraction, abandoning a water layer, using the water for washing an ether layer till the pH is equal to 7, further using anhydrous magnesium sulfate for drying, carrying out atmospheric distillation for removing a solvent to obtain a compound III, using a raney nickel catalyst for carrying out catalytic hydrogenation on the compound III in the methanol, removing the methanol, and carrying out decompression distillation, thereby obtaining the delta-lactone.